If $x \diamond y = x+8y$ and $x \oplus y = 3x-4y$, find $(-1 \diamond 1) \oplus -1$.
Solution: First, find $-1 \diamond 1$ $ -1 \diamond 1 = -1+(8)(1)$ $ \hphantom{-1 \diamond 1} = 7$ Now, find $7 \oplus -1$ $ 7 \oplus -1 = (3)(7)-(4)(-1)$ $ \hphantom{7 \oplus -1} = 25$.